1. Field of the Invention
The present invention relates to a method and apparatus for a camera, and more particularly to a method and an apparatus for controlling a privacy mask display.
2. Description of the Related Art
A monitoring camera, a camera or video camera, may be installed to capture an image of a target object being monitored in a security-enforced area. The captured monitored image can be stored in a digital video recorder (DVR), which has been made commercially available in recent years. The monitored image captured by the monitoring camera may contain privacy-related data such as facial images of unspecified persons, thereby generating concerns about invasion of privacy. FIG. 1a illustrates an example of a monitoring camera having panning and tilting capability.
To protect the privacy of an unspecified person possibly exposed by capturing the monitored image, a method has been proposed which overlaps a privacy mask (or a masking block) such as a mosaic image with the monitored image of a target object. This method overlaps an image containing a privacy mask with the monitored image, and displays the two images together so that the privacy mask selectively masks a target object to be privacy-protected in the monitored image.
While photographing or video recording an area A at a tilt angle of about 60°, the monitoring camera 100 may be rotated 180° in the panning direction as shown in FIG. 1b, or be rotated about 60° in the tilting direction as shown in FIG. 1c, to photograph an area B opposite to the area A relative to the monitoring camera 100.
However, if the monitoring direction of the monitoring camera 100 is changed through the panning operation as in the former case, it takes a relatively long time to rotate the pan motor by 180°. If the monitoring direction of the monitoring camera 100 is changed through the tilting operation as in the latter case, it takes a relatively short time to rotate the tilt monitor by a total of about 60° because of the smaller rotation angle. However, the image captured by the monitoring camera 100 is inverted top to bottom owing to the top to bottom inversion of the monitoring camera 100 as soon as the monitoring camera 100 exceeds a 90° angle position of a vertical plane in the tilting direction (FIG. 1d). Thus, in the former case, the image is not inverted while in the latter case, the image is inverted.
If the tilt angle is greater than 90° as shown in FIG. 1d, the image is inverted from top to bottom and from left to right, by rotating the monitored image 180° with respect to a CCD center axis.
Meanwhile, the monitoring camera 100 is also able to perform zooming to adjust a size of the monitored or captured image. The monitored or captured image may be enlarged/reduced depending on whether the monitoring camera 100 is zoomed in/zoomed out. Therefore, the monitoring camera 100 is able to independently pan, tilt, and zoom in accordance with a user's request or automatically based on sensor, detectors and/or prescribed programming to monitor the place where the monitoring camera 100 is installed to observe various areas of the place of installation, such as a security area.
For such a monitoring camera 100, a privacy mask of a predetermined size is overlapped over the a monitored image at a proper region so that a specified target object requiring privacy protection is not exposed to the captured image frame, where a captured image may be one of a photograph or video.
While the privacy mask is overlapped over the monitored image or the specified target object contained in a captured image frame or the monitored image, if the monitoring camera 100 is rotated in the panning or tilting direction or is zoomed in or out, then the monitored image of the specified target object in the captured image frame is shifted and/or enlarged/reduced corresponding to the rotation and zooming. Corresponding to this, the position and/or size of the privacy mask is adjusted when the monitored image is shifted and/or enlarged/reduced.
However, in spite of the adjustment of the position and/or size of the privacy mask in response to the rotation or zooming of the monitoring camera 100, the adjusted privacy mask may inaccurately mask the monitored image that is shifted and/or enlarged/reduced. In particular, when the monitoring camera 100 is zoomed in or out (change of a zoom ratio), inaccurate adjustment of the privacy mask may occur frequently.
In relation to the change of a zoom ratio of the monitoring camera 100, the inaccurate adjustment of the privacy mask may be caused by the fact that the CCD center axis does not coincide with the lens optical center axis. The CCD center axis and the lens optical center axis of the monitoring camera 100 may not coincide physically because of improper mounting of the CCD on a printed circuit board (PCB), misalignment of the lenses, or the like.
To lessen such problems resulting from the non-coincidence between the CCD center axis and the lens optical center axis, a microcomputer of the monitoring camera 100 enlarges or reduces the privacy mask and simultaneously shifts the privacy mask relative to the lens optical center axis, instead of the CCD center axis, when the zoom ratio changes.
However, if the monitoring camera rotates in the tilting direction and the tilt angle becomes greater than 90° to cause inversion of the image, while the zoom ratio also changes, then the center of rotation of the captured image may become different from the center of shift of the privacy mask. Consequently, the privacy mask may be inaccurately adjusted, and will fail to completely mask the monitored image and/or the specified target object.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.